1. Field of the Invention
The present invention relates to electronic input terminals for entering access codes to open a locked door or the like. More specifically, the invention relates to such terminals in which a rotatable and axially movable knob is used to enter a coded sequence of numerals or alphanumeric symbols.
2. Description of the Prior Art
It is known to provide a door with an electronic input terminal having a knob that can be manipulated through two degrees of movement, rotation and axial displacement, to select and enter elements of a coded sequence. See for example U.S. Pat. Nos. 4,899,562 and 4,745,784. The knob is rotated to select a number and is then pushed to contact a circuit board which generates an electrical signal to a solenoid. The solenoid controls movement of a member which releases the lock to allow the door to be opened.
The electronic door lock of the '562 patent includes a liquid crystal display. The knob is rotated to select a number corresponding to an element of a coded sequence, and is then pushed to input the number. The inputted numbers are displayed by the liquid crystal display. Because the knob of the lock is also used to retract a bolt, the rotation of the knob is severely limited. As a result, the knob can only be used to select from ten digits. Additionally, the numbers selected are not displayed until after they have been inputted to the reader circuit.
SUMMARY OF THE INVENTION
The present invention provides an electronic alphanumeric input terminal which is used to enter numerals or alphanumeric symbols corresponding to a coded sequence to unlock a door or the like. The input terminal communicates with a microprocessor in which are stored valid entry codes for comparison to the numerals or symbols entered at the terminal.
The input terminal of the present invention includes several safety features to prevent undesired viewing of the numerals or symbols that are entered. Only one character, which as used herein includes numerals or alphanumeric symbols, is displayed at any point in time to prevent observation of the entered sequence.
The input terminal initially displays a random character which the user increments or decrements by rotating a knob to arrive at a selected character. Once this selected character is obtained, it is input by pushing the knob inwardly. Upon inputting of the selected character, the terminal displays a different random character in its place. This prevents observation of the selected character, and also prevents deduction of an entry code by observing a sequence of knob rotation, since the necessary rotations to arrive at the correct input will be random.
In one embodiment of the present invention, there is provided a display space for each element of the coded sequence. The user increments or decrements the random character displayed through clockwise or counterclockwise rotation of the knob and then depresses the knob to input the selected character.
The terminal then displays a blocking character, such as the letter X, in the corresponding display space once the selected character has been entered. This blocking character confirms to the user that the character selected has been entered, and also prevents observation of the selected character while the user manipulates the knob to input the remaining characters of the coded sequence. As each selection after the first is input, a blocking character is displayed in its place so that only one selected character is displayed at any one point in time.
In another embodiment, the present invention includes a single character display which initially presents the user with a first random character. This character is incremented/decremented to arrive at a first selected character corresponding to one entry of a coded sequence. The user inputs the first selected character and the terminal then displays a second random character. The second random character is then adjusted to arrive at a second selected character which corresponds to another entry of the coded sequence. With this arrangement, once the selected character is inputted by the user it is no longer displayed. Thus, observation of the sequence of selected characters is prevented.
This embodiment may have indicators corresponding to the positions of the elements of the entered sequence to show that a character has been input in a particular position. This allows the user to keep track of the characters which have been entered without display of those characters.
The input terminal of the present invention provides a secure means of accessing doors or the like and is of a reduced size suitable for limited space applications and easy installation. Security is enhanced by use of the random number generation by the terminal. This feature prevents an unauthorized observer from memorizing any sequence of knob rotation by a user to thereby deduce the entry access code.